Whenever I add trees from Endor to my map, and go to play it, right when it's done loading the map, the game crashes and turns off.

Is there something wrong with the Endor trees, or is it just I am using too many?

It's quite possible that you're using too many, because I've never had a problem with using the Endor trees, apart from the tops of them are chopped off, LoL.

There is a probelm with the third tree. Get rid of all trees that say "end_prop_tree3" or something like that.... the same thing happened to me.